Molecular phylogeny of euglyphid testate amoebae (Cercozoa: Euglyphida) suggests transitions between marine supralittoral and freshwater/terrestrial environments are infrequent

Abstract

a b s t r a c tMarine and freshwater ecosystems are fundamentally different regarding many biotic and abiotic factors. The physiological adaptations required for an organism to pass the salinity barrier are considerable. Many eukaryotic lineages are restricted to either freshwater or marine environments. Molecular phylogenetic analyses generally demonstrate that freshwater species and marine species segregate into different sub-clades, indicating that transitions between these two environments occur only rarely in the course of evolution. It is, however, unclear if the transitions between freshwater and environments characterized by highly variable salinities, such as the marine supralittoral zone, are also infrequent. Here, we use testate amoebae within the Euglyphida to assess the phylogenetic interrelationships between marine supralittoral and freshwater taxa. Euglyphid testate amoebae are mainly present in freshwater habitats but also occur in marine supralittoral environments. Accordingly, we generated and analyzed partial SSU rRNA gene sequences from 49 new marine/supralittoral and freshwater Cyphoderiidae sequences, 20 sequences of the Paulinellidae, Trinematidae, Assulinidae, and Euglyphidae families as well as 21 GenBank sequences of unidentified taxa derived from environmental PCR surveys. Both the molecular and morphological data suggest that the diversity of Cyphoderiidae is strongly underestimated. The results of our phylogenetic analyses demonstrated that marine supralittoral and freshwater euglyphid testate amoeba species are segregated into distinct sub-clades, suggesting that transitions between these two habitats occurred only infrequently.

Deep sequencing uncovers protistan plankton diversity in the Portuguese Ria Formosa solar saltern ponds

“…As for bacteria (Lozupone and Knight 2007;Logares et al 2009Logares et al , 2010, animals and plants (Lee and Bell 1999;Vermeij and Dudely 2000), salt is a strong environmental barrier for protists (Logares et al 2009;Bråte et al 2010;Heger et al 2010;Forster et al 2012;Dunthorn et al 2014b), demanding specific adaptation mechanisms (McGenity and Oren 2012). It is therefore reasonable to assume investigations of high salt environments are likely to discover new evolutionary lineages in the eukaryotic tree of life, hitherto unseen in other aquatic habitats.…”

Environmental DNA COI barcoding for quantitative analysis of protists communities: A test using the Nebela collaris complex (Amoebozoa; Arcellinida; Hyalospheniidae)

“…The advantage of the COI-based metabarcoding approach is to provide a much finer level of taxonomic resolution than that the SSU rRNA gene usually used in environmental DNA studies. COI has also been shown to give high taxonomic resolution in many microbial eukary-otic groups (Barth et al 2006;Chantangsi et al 2007;Heger et al 2010;Lin et al 2009;Nassonova et al 2010). For exam-ple, in the Hyalospheniidae, SSU rRNA does not allow to discriminating among closely related taxa (Lara et al 2008) while COI does (Kosakyan et al 2012(Kosakyan et al , 2013.…”

“…As the identification of many putative taxa is highly dependent on the observer, results are often difficult to compare among studies. This problem, often referred to as cryptic diversity, is recurrent in eukary-otic micro-organisms (Beszteri et al 2005;Heger et al 2010;Koch and Ekelund 2005;Kosakyan et al 2012;Kucera and Darling 2002).…”

Effect of taxonomic resolution on ecological and palaeoecological inference – a test using testate amoeba water table depth transfer functions

“…In the light of current taxonomic studies revealing a wealth of unsuspected diversity in testate amoebae (Heger et al, 2010;Heger et al, 2011;Kosakyan et al, 2012Kosakyan et al, , 2013, it would be interesting to perform the opposite experiment, aiming at higher taxonomic resolution than has been generally been applied. If such "cryptic" (morphologically undistinguishable) or "pseudocryptic" (with very subtle morphological differences) species also differed in their ecological optima the performance of transfer function might be substantially improved.…”